• 전기학회논문지
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• 제65권4호
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• pp.652-658
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• 2016

In practical control systems differences between nominal and real systems arise from internal uncertainties and/or external disturbances. This paper presents a model-based low-order disturbance observer for a sinusoidal disturbance with unknown constant offset. By using the disturbance model of a biased harmonic signal, the proposed method can successfully estimate the biased sinusoidal disturbance with unknown amplitude and phase but known frequency. At the first stage of the observer design, a model-based disturbance observer is designed when all the system states are measurable. Next, a sufficient condition is presented for the proposed observer to estimate the sinusoidal disturbance with a minimal-order additional dynamics using only output measurement. Comparative computer simulations are performed to test the performance of the proposed method. The simulation results show the enhanced performance of the proposed disturbance observer.

• 전기학회논문지
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• 제56권10호
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• pp.1844-1851
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• 2007

This paper presents methods for the compensation of sinusoidal disturbances with unknown amplitude, phase, and time-varying frequency in nonlinear systems. In the previous disturbance accommodation methods, the sinusoidal disturbance with unknown time-invariant frequency was considered. In the proposed method, the disturbance with unknown time-varying frequency is compensated. As for the control structure, two control inputs are designed separately in such a way that one of them is designed for the nonlinear system control without considering the disturbance, and the other one uses the disturbance estimate obtained from the disturbance accommodating observer. The stability analysis is done considering the disturbance estimation error and the numerical simulation demonstrates the proposed approach.

• 제어로봇시스템학회논문지
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• 제8권8호
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• pp.682-690
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• 2002

This paper presents an output feedback controller design method for uncertain linear systems with sinusoidal disturbance of uncertain frequencies. The controller needs to compensate for the performance deterioration due to the uncertain frequencies of sinusoidal disturbance. To this end, we introduce a virtual system including the dynamics corresponding to the uncertain frequencies and design a controller which minimizes the output difference between the virtual system and the closed-loop system. In other words, the controller is designed so that the closed-loop system approximates the virtual system. The feedback controller is achieved by solving an LMI optimization problem involving a robust $H_{\infty}$ constraint. The advantages of the proposed design method are examined by comparing it with a design method that only minimizes the $H_{\infty}$ norm of the transfer function between the sinusoidal disturbance and the output. The proposed design method is applied to the track-following system of rewritable optical disk drives and is evaluated through an experiment.

• 전기학회논문지
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• 제59권5호
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• pp.966-971
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• 2010

An adaptive state observer is presented for a class of LTI systems that have a sinusoidal disturbance in the measurement output. Adaptation rules are developed for identifying the unknown sinusoidal disturbance signal from the system output. For the application of the identification result to the state estimation problem, the sinusoidal signal with arbitrary initial phase has been considered in this paper. In order to test the performance of proposed algorithm, comparative computer simulations have been carried out with an existing robust observer. The simulation results show the effectiveness of the proposed method.

• Journal of Power Electronics
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• 제9권5호
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• pp.791-799
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• 2009

This paper presents a time-varying sinusoidal disturbance compensation method (based on an adaptive estimation scheme) for induction motor drives fed by a matrix converter. In previous disturbance accommodation methods, sinusoidal disturbances with unknown time-invariant frequencies have been considered. However, in the new method proposed here, disturbances with unknown time-varying frequencies are considered. The disturbances can be estimated by using a disturbance accommodating observer, and an additional control input is added to the induction machine drive. The stability analysis is carried out considering the disturbance estimation error and simulation results are shown to illustrate the performance of the proposed solution.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1212-1217
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• 2006

This study is concerned with static and sinusoidal disturbance rejection for a single periodic input disturbance with known period. In the area of active elimination of a disturbance force, the control input should have two different kinds of gains: one is to deliver a stable control and the other is a force component to cancel the external disturbance force. In this paper we employ a simple state feedback control law to make the balance beam stable and employ a linear observer to estimate the states which represent the external disturbance force components. Simulation results verify our proposed control method to reject a static and sinusoidal disturbance force.

• 전기학회논문지
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• 제64권5호
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• pp.751-754
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• 2015

This paper deals with a robust speed control problem of a vertical one-link manipulator in the presence of parameter uncertainties and unknown input disturbance. Uncertain load weight causes an additional sinusoidal disturbance in the rotation of the link. In order to improve the robustness against parameter uncertainties and external input disturbances, this paper employs an internal model-based disturbance observer approach. Comparative computer simulations are performed to test the performance of the proposed controller. The simulation results show the enhanced performance of the proposed method.

• 한국소음진동공학회논문집
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• 제16권3호
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• pp.283-290
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• 2006

이 연구는 알고 있는 단일 주기를 갖는 정적 및 주기적 외란의 제거에 대해서 다룬다. 자기력 부상시스템에서 외란력을 능동적으로 제거하기 위해서는 제어 입력이 두 가지 다른 이득 값을 가져야 한다. 하나는 시스템의 안정적 제어를 위한 부분이고 다른 하나는 외부로부터 시스템에 영향을 미치는 외란력의 제거를 위한 부분이다. 본 논문에서는 평형 빔을 안정 적으로 제어하기 위해서 간단한 상태 궤환 제어기를 채용하며, 외부로부터 시스템에 영향을 미치는 외란 성분을 추정하기 위해서 선형 관측기를 채용한다. 또한 자속의 궤환에 의해서 구성된 제어 전류는 관측기에 의해서 관측된 외란력과 외란력을 억제하려는 전자석의 힘의 차로 나타나며 이들 관계는 선형성을 유지한다. 이 선형성은 본질적으로 비선형성을 갖고 있는 자기력 부상 시스템에 대한 수치 해석적 용이함을 제공하며 이 논문에서 다루는 정적 및 주기외란의 제거를 위해서 우수한 성능을 발휘한다. 모의시험 결과는 제안된 제어 기법에 의한 정적 및 주기적 외란의 제거를 입증한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.452-457
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• 2003

An add-on type output regulator is proposed in this paper. By an add-on controller we mean an additional controller which operates harmonically with a pre-designed one. The role of the add-on controller is to reject a sinusoidal disturbance of unknown magnitude and phase but with known frequency. Advantages of the proposed controller include that (1) it can be used only when the performance of disturbance rejection needs to be enhanced, (2) when it is turned on or off, unwanted transient can be avoided (i.e., bumpless transfer), (3) it is designed for perfect disturbance rejection not just for disturbance reduction, (4) ability for perfect rejection is preserved even with uncertain plant model. This design may be promising for optical disc drive (ODD) systems in which disc eccentricity results in a sinusoidal disturbance. For ODD systems, the sensitivity function obtained by the pre-designed controller, which may have been designed by the lead-lag, $H_{\infty}$, or DOB (disturbance observer) technique, does not change much with the add-on controller except at the frequency of the disturbance. Since the add-on controller does the job of rejecting major eccentricity disturbance, the gain of the pre-designed controller does not have to be too high.

• 전기학회논문지
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• 제59권12호
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• pp.2278-2283
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• 2010

This paper deals with the pendubot control using disturbance observer. Experimental results for the motion of pendubot with balancing control show that the limit cycle can be attributed to the disturbance. Therefore, we propose the disturbance compensation method using by disturbance observer to compensate for the disturbance. Through the experimental results, the effectiveness of the proposed method is verified.